Dam



F. A. NOETZLI Dec. 15, 1931.

Filed Sept. 1'7, 192'! INVENTOR Patented Dec. 15, 1931 FRED A. nonrzm, or Los VANGELES, oALIronnrA Application filed September 17, 1927. Serial no. 220,197.

This invention relates, to the construction of concrete and masonry dams and the primary object of'the inven'tionis to provide a dam of this type which will be safer and less expensive and which can be built in a shorter period of time than dams such as heretofore constructed. 7

Most concrete and masonry dams as heretofore constructed have been ofthe gravity, arch, multiple arch or deck slab type. Some of these dams depend for stability upon the weight of the structure alone, such as gravity dams. Others, like arch and multiple arch dams, depend upon arch action, and in deck slab dams the water pressure is supported by slab or beam action;

In multiplearch and deck slab dams the water pressure is transmitted by means of arches or deck slabs upon buttresses. This transmission of stresses involves arch action or bending moments which may introduce large stresses in the deck and necessitates, in some cases, the use of reinforcing steel for taking care of tension stresses. The decks of these dams are usually thin and are subject to deterioration from frostLaction.

In many buttressed dams as built heretofore, including multiple arch dams, there have developed inthebuttresses cracks due to shrinkage and temperature deformations,

and also due to load conditions. 7 I

i The objects of my invention are," first, to build a dam comprising buttresses provided with joints tending to facilitate expansion and contraction of the buttresses; second, to

build such a dam of buttresses having en-' larged buttress heads for resisting the water pressure, and also to build such a dam of buttressessupporting an archeddeck, and

having joints in the buttress heads and in the arches tending to facilitate expansion and contraction of these members.

Otherobjects of my invention will be disclosed in the following detailed description. In the accompanying drawings, forming a part of, this specification, I Y

' Figure 1 is a schematicalelevation of the improved dam, looking-upstream.

Figure 2 1s a typical sideelevation of one buttress and buttress head, as seen from the line 22of Figure 1. Figure 3 is a horizontal section on the line 33 of Figure 2. Figure 4 is a section on the line 4-4 of Figure 1. v

Figure 5-is a horizontal section on the line 55 of Figure 4.

Referring to Figure 1. The dam shown comprises buttresses B, some of the buttresses having an enlarged buttress head 6 toward the up-stream side of the buttress wall 7, and others having arches A. The dam shown in Figure 1 hasbuttres' ses with buttress heads in the deeper part of-thecanyon across which the dam is built, audit hasother buttresses with arches, at both wings of the dam where the height of dam'is smaller than in the center. It is to be understood, however, that I may build my improved dam of buttresses either with buttress heads or with arches, or with any other combination, including wings of gravity section or earth-fill, as the geology of the dam site and economic considerations may make it appearto be best suited.

. Figure 2 isa side elevation of a buttress of myim'p roved dam and shows joints 8 and 9,

and joints 10, in,the buttress wall, andin the buttress head, respectively. The joint 8 starts at a point near the foundation and extends upward towards the lip-stream side of the buttress. The theory of the princi a1 stresses in buttresses of dams indicates t at thereare certain maximum principal stresses in the buttresses of a dam which for a full reservoir are substantially perpendicular to the up-stream face and nearly parallel to the downstream face. (SeeWegmann, The Design and Construction of Dams, 8th edition, Part IV, A mathematical discussion and description of multiple arch dams, by the writer.) Certain minimum principal stresses for the same load conditions areat all points perpendicular to the direction of the corresponding maximum principal stresses. I have found in investigating many of the existing buttressed dams that the minimum principal stresses for a full reservoir are often in excess of 100 pounds per square inch tension and may therefore have been at least partly responsible for the cracks in some of these dams. In other buttressed dams cracks have formed already during constructon, giving evidence of internal temperature and shrinkage stresses. Such shrinkage cracks have occurred in spite of strong steel reinforcement. inthe buttresses, and some of these cracks are of irregular zig zag shape and occur in planes of high shear, thus endangering seriously the stability of the buttresses.

One of the objects of my invention is to localize the shrinkage cracks by providing special expansion joints 8 and 9 asshown on Figure 2. These oints are arran'gedin such awaythat the minimum principalstresses in the buttress with reservoir full} are at all .elevations substantially perpendicular to the joints, and if these minimum. principal stresses should be tensioned they would merely tend to open the joints. This wouldnot affect the stability ofthe damimaterially 'because there would be little, if' any ,.shear, in thepjlane of the joints,-and thetension across the joint wouldbe relieved.

The lines of the maximum principal stress are generally at a flat-ter slope than the clownstream face. of the buttress Consequently the joints 8 and 9 willgenerallybeat a greater distance from the down streamface of the buttress at upper elevations than atlower elevations:- The angle w in Figure 2is therefore generallysmaller than. the angle 00. There may be aplurality of joints 8. and 9 especially in the-case of high. dams.

Referring. to Figure 3, the oint 8 is shown to extend throughthe entire thickness of the buttress wall. The-joint 8 is preferably providcdwith a key oif-setK which should prevent the'lat'eral movementof one part of the buttress wall relatively tot'he other. part. I provide suitable means for preventingbonding of the concrete across the joint such as painting one side of: the. joint with coal tar, asphalt, or other material.

I. may construct a joint. extending only partly through the. thickness of the wall as shown by joint 9 in Figure 3. A part of the thickness of the. wall, inthe present case, approximately the middle half, would then be solidand transmit a moderate amount of stresses. In case suiiicient tension should occur, thejoint would be likely to break also in the solid middle half of the buttress wall, the outer one quarter thicknesses providing a plane of minimum resistance. Consequently,

in case the' joint should open up it wouldv be along pre-determinedlines in the place where the designer should like to have it as it would do there the minimum damage. In. order to facilitate construction, I may provide a thin sheet of tar paper, burlap, or other suitable 'material, extending. entirely or part way through the thickness of. the buttress and in the direction of thc'joint,,and hold it properacross the plane of the joint, or I may stop some orsalliofthe reinforcing bars on both sides of the joint. The bars 11 extending across the joint will not defeat the purpose of my invention, inasmuch as these bars will stillpermitof"aslightopening and closing of the joint, but the bars will prevent excessive movement of the joint.

I may construct certain portions of my improved dam of buttresses with enlarged buttress heads,.substantially as described in my application for Letters Patent, Serial No. 122,141, filed July 3, 1926. The upstream face of the buttress head.6 has such a shape that the force of the water pressure is transmitted onto the buttress wall 7 through the buttress head in the same direction to that of. the water pressure upon the up-stream face. I may provide the up-stream face of the buttress head 6 with a suitable waterproofingmaterial.lV, such as asphalt, roofing paper, or the like, and protect the waterproofing and up-stream face with. a concrete slab. C of. suitable thickness. Inasmuch as there may be water seeping through this slab,.I may provide drainage canals D and drain holes, or other suitable means, for collecting. 2111(1tllSP0S111 Of thisseepage water.

Referring. now to Figure f, a section of my improved damis shown. on the line l-t of Figure 1.

Figure. 5 shows a section on-the line 55 of Figure. 4:. I may construct some of the buttresses of my improved dam with arches A springing. from the up-stream face of the buttress. Inorder to increase the theoretical rise of these arches and increase thereby their flexibility, thus decreasingthe temperatures stresses in the arches, I provide a joint 1'2between the arches, this joint being located substantially on the center line of the buttress B. The joint 12. may be formed by a sheet of roofing paper or other material, suit-- ably held in place during the concreting of the arches. The joint may therefore be formed without the use of' additional form work.

In many multiple arch dams constructed in the past the pressure of the arches upon the buttress walls is so large that inclined tension stresses occur in the portions of the the buttress Walls by increasing the thick ness of the buttress wall toward the up-stream side. This thickening of the buttresswall is not necessary .over the entire lengthof the buttress, but a gradual increase in thickness from a point between the up-stream and clown-stream sides of the buttress toward the up-streamside, is sufficient and most economical.

In constructing my improved dam I erect suitable forms for the buttress wall 7, and I also provide a thin sheet 13 of suitable ma terial preferably held to the forms and held in place'during concreting of the buttress wall 7. The sheet 13 may be of roofing paper, burlap or other suitable material. It, may extend partly or wholly through the thickness of the buttress wall 7, preferably at approximately a right angle to the'forms, and said sheet 13will extend substantially in the direction of the joints 8 from a point near the foundation of the buttress Wall 7 upwards and towards the upstream side of the buttress wall 7. Concrete is then poured into the forms and on both sides of the sheet 13. This construction is preferably made in steps, corresponding to pourings of concrete of 4 to 8 feet of height.

I may also form the joint 8 in the manner that I pour, first a portion of the buttress wall 7 which is upstream of the joint 8, then making suitable provision, by painting, or otherwise, for preventing the bonding of the concrete across the joint 8, or across certain portions of the joint 8, and then pouring the portion of the buttress wall 7 which is downstream of the joint 8. The joint 8 is substantially parallel to the direction of the maximum principal stresses when the reservoir is full. A point of the joint 8 near the upstream side of the buttress wall 7 is therefore at a greater distance from the downstream face of the buttress than a point of the same joint 8 near the foundation of the buttress wall 7. I

I construct certain portions of my improved dam by building a buttress wall 7 and an enlarged buttress head 6, certain parts 1 1 of which extend laterally beyond the buttress wall 7, and I place and hold properly in position during concreting a sheet 15 of suitable material in the buttress head 6, this sheet to extend substantially perpendicularly to the up-stream face of the buttress head 6, and reaching from the Lip-stream face to the downstream face of the parts 14: of the buttress head 6. The joint 1.0 which is formed by the-plac ing of a sheet 15 in the part 14 of the buttress head will tend to facilitate an irregular expansion and contraction of the buttress head 6 and thus tend to eliminate the danger of cracks forming in the buttress head 6 in a vertical direction.

I claim:

1. In a dam forming areservoir, a buttress and 9, and extend rovided with an ex ansion 'ointextendin D 2. In a dam a buttress provided with an expansion joint extending from a point near the rip-stream side to a point near the foundation of said buttress, said point near the upstreamside being at a greater distance from the down-stream face of said buttress than said point near the foundation. r

In a dam a but-tress provided with an expansion joint forming an angle with a horizontal plane,said angle being at practically allelevations smaller than the corresponding angle between the down-stream face of'said buttress and the horizontal. at the same elevations. V

4. In a dam a buttress provided with a plu- ,rality, of expansion joints extending from points near the lip-stream side'to points near the foundation of said-buttress, said points nearthe upstream side being at a greater distance from the down-stream faceof said buttress than -sai d points near the foundation. '5. In a dam formin a reservoir, a buttress with a plurality of oints extending from points nearthe up-stream face to pointsnear the foundation of said buttress, said points being substantially parallel to the direction of certain principal stresses in said'buttress when the reservoir is full.

6; In a concrete dam a buttress wall having an expansion joint, said jointv extending through the total thickness of said wall, a key off-set in said joint tending to prevent the lateral movement-of the parts of said buttress wall on either side of said joint.

7. "In adani, a buttress wall which is divided upon downwardly and rearwardly extending predetermined lines into sections, whijch'seetions are designed to function substantially independently of each other in sustaining their proportions of'the loads when the dam is loaded. I f j 8. In a dam, a buttress wall which isdivided upon predetermined lines into sections, said linesbeing substantially lines of maximum principal stresses in the wall when the damis fully loaded.

9. In a dam, abuttress Wall whichis divided upon predetermined lines into sections, said lines being substantially normal to the minimum principal stresses in the wall when the dam is fully loaded.

10. In a dam, a buttress wall which is divided upon downwardly and rearwardly extending predetermined weakened lines into sections, which sections are designed to function independently of each other in sustainingtheir proportions of the loads when the dam is loaded, and means preventing lateral displacement: of! said; sections. relatively to each other.

11. In a dam, a buttress wall: having a downwardly and rearwardly extending joint arranged alonga line parallel to certain maxi? mum prineip'al'stresses'in the wall when the dam isfullyjloaded, andreinforcing rods extending across. the joint.

12. In adam a buttress wall having a sheet of'suit able material embedded in the wall and extending partially therethrough in atransverse direction, said sheet serving to divide the wall into sections connected together by a weakened and relatively thin web whereby the sections may function practically independently of each other in sustaining stresses.

13.nIi1 a dama buttress wall having sheets ofs'suitable material extending inwardly from oppositesides of the wall. in opposition to each other but having their opposed edges inspacedrelation, said sheets serving to. divide the wall into sections connected together by a comparatively weak thin connecting web whereby. the sections may function practically independently of each other in sustainin g stresses.

14. In a dam, a buttress wall which is divided'by expansion joints disposed along predetermined lines into sections, said joints extendingdownwardly and rearwardly substantiallyparallel. to the direction of certain maximum principal stresses in the buttress wall when thedam is fully loaded, and reinforcing steel bars connecting said sections.

15; In a dam, a buttress wall which is divided uponpredetermined lines into sections, said lines being substantially parallel to the lines of. certain maximum principal stresses inthewallwhen the dam is fully loaded, and means for preventing other than relatively small movements of two adjoining sections with respect to each other.

16. In a dam, a wall extending substantially crosswise to the direction of the dam, said wall. being divided by predetermined areas of weakened bond into portions, said areas extending crosswise to the direction of said wall and extending substantially parallel to'lines of Zero shear in the wall when the dam is fully loaded.

17. In a dam, a buttress wall divided by an inclined expansion joint into sections, said expansion joint being arranged approximately parallel to a plane of Zero shear in the wall when the dam is fully loaded.

FRED A. NOETZLI. 

